The present invention relates to a cylindrical lock. More particularly it relates to an assembly which comprises a conversion kit for converting a knob operated cylindrical lockset to a lever lockset.
A very common lock used in the American market and in other markets is a fully cylindrical lockset which may have a five or six pin-tumbler cylinder in a standard configuration and/or a removable core cylinder. Such locksets come in ANSI series 1, which is a heavy-duty lock; and ANSI series 2 which is a standard duty and is the major commercial door lockset sold in the United States; and an ANSI series 3 which is a light commercial-duty lockset. These are all fully cylindrical locksets that were originally designed and patented by the Schlage Lock Company, many years ago.
There is a current and a future increasing demand and requirement for the provision of lever-operated locksets in situations where knobs have been used previously. One of the major reasons for this growing requirement is the growing attention to the needs of the handicapped. Certain handicapped persons can operate a lever handle lockset more easily than a knob operated lockset. In specific addition, the provisions of the Americans With Disabilities Act of 1990 has gone into effect. This provides a federal legislative standard of "providing a broad national mandate for the elimination of discrimination against individuals with disabilities". It includes discrimination in transportation, public accommodations, and the activities of state and local governments. This includes work sites, medical offices, retail establishments, theaters, federal buildings and other structures. It requires that there be barrier-free design and that the places of accommodation be readily accessible and usable. It is estimated that there are 42 million Americans with some degree of disability.
An American National Standard A 117.1-1980, Section 4.27.4 requires that there be door controls, and that the operating mechanisms shall be operable with one hand and shall not require tight grasping, pinching, or twisting of the wrists, and the force required to activate controls be no greater than 5 lbf. American National Standard A117.1-1980, Section 4.13.9, relating to door hardware, requires that locks have a shape that is easy to grasp with one hand and do not require tight grasping, tight pinching, or twisting of the wrist to operate. Lever-operated mechanisms are one of the preferred acceptable designs.
There is therefore a need for a retro-fit kit to enable existing cylindrical locks to be converted to lever-operated locksets. Previous attempts have been made. A serious difficulty with previous attempts relates to the fact that cylindrical locks have been solely for knob operation.
The springs that operate a cylindrical lock are very small. There are only two small compression springs, inside the lock, behind the retracting bar. These two small compression springs are suitable to operate a cylindrical knob lock since there is little torque and the two small compression springs can adequately return the knob and spindles to the original starting position, after the lock has been retracted.
When an attempt was made to add levers to existing unaltered cylindrical locksets, it failed for the following reasons. Since a cylindrical lock was manufactured solely for use with knobs, the construction did not accommodate problems that arise when using levers with a cylindrical lock such as:
(1) Lever sagging because of inadequate internal spring power. After continued use, the small normal internal compression springs in a normal cylindrical lockset would become fatigued and the lock would then sag to a position below the horizontal. Enough sagging would cause the lock to unlatch itself.
(2) The serious damage that can be caused to a normal ANSI Grade 1, 2 or 3 fully cylindrical lockset because of the relatively tremendous torque pressure of a commercial lever which is normally 5" long, compared with knobs which rotate on an axis and with little or no chance of creating enough torque on the internal parts of the lock that will cause it to break or become defective and/or inoperative.
Most of the parts of a conventional cylindrical lockset in ANSI Grades 1, 2 or 3 are of a stamped steel construction. The lock spindles on which the knobs and/or levers are mounted are stamped steel, formed into a cylinder shape. Internal parts like the retracting bar and other major parts of mostly all cylindrical locksets are also stamped steel.
When the cylindrical lock was invented, many years ago, it was not anticipated that it would be used with levers. The light stamped steel parts and construction are adequate and suitable for long and efficient use of the classic cylindrical lockset in ANSI Grade 1, 2 or 3 constructions only in knob locksets.
Even the classic ANSI Grade 1 pure cylindrical lockset is made of mostly stamped steel parts. Even ANSI Grade 1 locksets will not withstand the severe torque pressures of a full length commercial lever mounted in place of various styles of knobs.
Since a pure cylindrical lock contains no positive stops, the lock can be broken if more than a certain amount of torque force is exerted on the lockset when rotating the spindles by either knob or lever operation. Since no positive stops were designed into the basic construction of a conventional cylindrical lockset in any of the three grades, whenever a force created by the rotating of the spindles is greater than a certain amount, it will break up and destroy the lockset. Such breakage and damage will result in distortion of the tubular spindles on which the levers and/or knobs are mounted; breakage of internal stamped steel parts such as the cam on the end of the spindle which activates the retracting bar. Because of the lack of positive stop, there are various other ways that a cylindrical lockset can be broken when using lever operation, instead of knob operation.
Another serious problem that hindered lock manufacturers from successfully converting a conventional ANSI Grade 1, 2 or 3 cylindrical lockset from knob to lever use was the need of a compensating rose feature which is the feature that helps to mount and hold the lock body in the center of the door. The compensating rose feature is necessary because of varying door thicknesses.
Because of the presence of a compensating outside rose on an ANSI Grade 2 or 3 fully cylindrical lock and/or compensating roses on both sides of an ANSI Grade 1 fully cylindrical lockset, it was not possible for lock manufacturers to add spring loaded rosettes to help to increase the spring power in order to help to eliminate the possibility of lever sagging, caused by the increased torque created by a commercial length lever, compared with the very low torque on a cylindrical lockset operating by the rotation of knobs.
Also, the problem of the adding of positive external mechanical stops to the lockset to prevent lock breakage caused by the severe torque when the lock spindles are rotated by the levers could not be eliminated or solved.
In recent years, some lock manufacturers have designed a cylindrical lock with levers, but these locks are not the pure, classic, unaltered, cylindrical lock construction. Instead, in order to try to overcome some of the serious constructional and operating problems, many cumbersome additional parts were added. Still, the resulting products have not totally eliminated all of the existing problems when using a cylindrical lockset with levers, instead of knobs. None have complete positive stops which will protect the basic lock mechanism from being broken or damaged.
Furthermore, because of the additional parts that have been added, such a lockset is much more difficult to install in the door since it requires the disassembling and reassembling of many parts, as compared with the few parts that need to be disassembled and reassembled on the basic construction in a pure cylindrical lockset. It does not result in the most constructionally sound and most efficiently operating lever type cylindrical lockset available. It cannot be retrofitted on all brands of cylindrical locks.